Evaluation ofLegionella pneumophilacontamination in Italian hotel water systems by quantitative real-time PCR and culture methods

Abstract

Aims: This study was designed to define the extent of water contamination by Legionella pneumophila of certain Italian hotels and to compare quantitative real‐time PCR with the conventional culture method. Methods and Results: Nineteen Italian hotels of different sizes were investigated. In each hotel three hot water samples (boiler, room showers, recycling) and one cold water sample (inlet) were collected. Physico‐chemical parameters were also analysed. Legionella pneumophila was detected in 42% and 74% of the hotels investigated by the culture method and by real‐time PCR, respectively. In 21% of samples analysed by the culture method, a concentration of >104 CFU l−1 was found, and Leg. pneumophila serogroup 1 was isolated from 10·5% of the hotels. The presence of Leg. pneumophila was significantly influenced by water sample temperature, while no association with water hardness or residual‐free chlorine was found. Conclusions: This study showed a high percentage of buildings colonized by Leg. pneumophila. Moreover, real‐time PCR proved to be sensitive enough to detect lower levels of contamination than the culture method. Significance and Impact of the Study: This study indicates that the Italian hotels represent a possible source of risk for Legionnaires’ disease and confirms the sensitivity of the molecular method. To our knowledge, this is the first report to demonstrate Legionella contamination in Italian hotels using real‐time PCR and culture methods.

Current and Emerging Legionella Diagnostics for Laboratory and Outbreak Investigations

“…These methods do not discriminate between free nucleic acids, either in solution or amoeba associated; nucleic acids from dead or dying bacteria; and/or viable but nonculturable (VBNC) legionellae. This is evidenced in environmental studies that detected a higher level of bacterial DNA than was corroborated by culture and where the persistence of Legionella DNA after multiple rounds of remediation resulted in no detectable culture growth (183,338,341,342,384). As a consequence, PCR has a low positive predictive value (PPV) for legionellae compared to that of culture methods in environmental settings; conversely, PCR has a high negative predictive value for viable Legionella in the same samples (Ն97%) (341,343).…”

“…Since the mainstream introduction of real-time PCR, numerous groups have evaluated the efficacy of nucleic acid detection alongside culture and other established methods. Assuming proper bioinformatics and primer/probe design and stringency, most NAAT-based assays are highly specific (close to 100%), and the growing consensus is that the sensitivity of PCR (both conventional and real time) is equal to or greater than that of culture-based detection using specimens from the lower respiratory tract or environmental water samples (286,(335)(336)(337)(338)(339)(340)(341)(342)(343)(344). Notably, the success of both PCR and culture for LD diagnosis is positively correlated with disease severity.…”

Prevalence ofmipvirulence gene and PCR-base sequence typing ofLegionella pneumophilafrom cooling water systems of two cities in Iran

“…7 Furthermore, 42% of Italian hotels water cooling systems of different sizes were contaminated by L. pneumophila. 8 Prevalence of L. pneumophila in water distribution systems in hospitals and public buildings of the Lublin region of eastern Poland was found to be 166 (74.77%) of hot water samples. 9 In other study, more than 1100 cases of legionellosis in Japan, caused by contaminated artificial whirlpool spas or natural hot springs were presented in Infectious Agents Surveillance Report 2014.…”

Comparing Efficiency Between Conventional and Molecular Methods for Detecting Legionella pneumophilia in Dental Unit Waterline Systems

“…The advantages of molecular methods, particularly real time PCR, are as follows: 1) isolation of VBNC, 2) detection of L. pneumophilia at very low concentrations, 3) rapid and sensitive identification of L. pneumophilia, and 4) better manipulation of large amounts of samples [13][14]. Real Time PCR can also determine the presence of non-cultivable Legionella spp., especially VBNC types [15].…”